What are all those people staring at? What do they hope to see in those finely textured posters, beyond the almost random display of little flowers or paint splotches? "Look deeper into the picture." "Look beyond the surface." "Cross your eyes." "Blur your vision." Not since Rubic's Cube has a puzzle or game engaged and fascinated the public as have the currently faddish 3D illusions on display in bookstores and shopping malls across the country. For many the exercise ends in frustration, seeing nothing beyond the surface images. Could it be a case of mass hypnosis or "The Emperor's New Clothes"? For those who see the three dimensional images pop into view, there is surprise, pleasure, and wonder. Having had experiences of both types, we sympathize with those who have decided they have better things to do than stare off into space. But in fact knowing how the pictures are created, understanding the elementary geometry and optics of stereographic vision, makes it much easier to see the images.